It is known that the electrical resistance of skin is controlled largely through the nervous system. Canadian Patent No. 1,254,269 issued May 16, 1989 to Woodley et al. discloses a diagnostic device based upon resistance measurements of the skin which is used to detect abnormal areas of the body where there is pain or sympathetic disfunction. U.S. Pat. No. 4,966,158 issued to Honma et al. discloses a device having two probes which measures the moisture content retained in the skin both in the keratinous layer and also in the deeper layer so as to provide information as to the condition of the skin. Patent Cooperation Treaty Application No. PCT/GB90/01991 discloses a device having a common probe and a reference probe. The measurement of resistance is switched between a common probe applied to an area of skin under test and a reference probe located on the identical area on the other side of the body. A difference in the readings indicates a damaged area of the skin. Thus, known devices measure only one parameter of the skin.
In order to be able to cross correlate different types of measurements of a given area and thus obtain confirmation of the condition and a more accurate diagnosis, it would be useful to be able to measure several different parameters simultaneously. Technically, one could first apply a device to measure resistance to a particular area and then one designed to measure moisture. However, such an approach would be impractical because not only could the condition of the area under test change from one measurement to the other, but positioning the probe on precisely the same area for both measurements would be difficult if not impractical. Secondly, many such measuring devices require measurements to be made using two separate probes applied to two separate but corresponding sides of the body.
Accordingly, it is an object of the invention to provide a method and apparatus for simultaneously measuring at least two different parameters of the skin.